IOSHA does not investigate random acts of violence – this is a police matter. Under certain circumstance, IOSHA does investigate workplace violence where employer policies may have put certain employees at a higher degree of risk. Examples might include pizza delivery drivers or cashiers at 24-hour markets. In these cases, for example, employer cash handling policies might contribute to an employee's vulnerability and thus be subject to review by IOSHA.
The US Department of Labor has issued "Recommendations for Workplace Violence Prevention Programs in Late-
Night Retail Establishments" (OSHA 3153), which may be downloaded from http://www.osha.gov/Publications/osha3153.pdf.
Another document which may be of interest is "Guidelines for Preventing Workplace Violence for Health Care & Social Service Workers" (OSHA 3148). This document may be downloaded from http://www.osha.gov/Publications/osha3148.pdf.